The Wnt signaling pathways are a group of signal transduction pathways made of proteins that pass signals from outside of a cell through cell surface receptors to the inside of the cell.
Wnt proteins are secreted glycoproteins with a molecular weight in the range of 39-46 kD, whereby in total 19 different members of the Wnt protein family are known (McMahon et al., Trends Genet. 8, 1992, 236-242). They are the ligands of so-called Frizzled receptors, which form a family of seven-transmembrane spanning receptors comprising 10 distinct subtypes. A certain Wnt ligand can thereby activate several different Frizzled receptor subtypes and vice versa a particular Frizzled receptor can be activated by different Wnt protein subtypes (Huang et al., Genome Biol. 5, 2004, 234.1-234.8).
Binding of a Wnt to its receptor can activate two different signaling cascades, one is called the non-canonical pathway, which involves CamK II and PKC (Kuhl et al., Trends Genet. 16 (7), 2000, 279-283). The other, the so-called canonical pathway (Tamai et al., Mol. Cell 13, 2004, 149-156) regulates the concentration of the transcription factor β-catenin.
In the case of non-stimulated canonical Wnt signaling, β-catenin is captured by a destruction complex consisting of adenomatous polyposis coli (APC), glycogen synthase kinase 3-β (GSK-3β), Axin-1 or -2 and Casein Kinase 1α. Captured β-catenin is then phosphorylated, ubiquitinated and subsequently degraded by the proteasome.
However, when a canonical Wnt activates the membrane complex of a Frizzled receptor and its Lipoprotein 5 or 6 (LRP 5/6) co-receptor, this leads to the recruitment of disheveled (Dvl) by the receptors and subsequent phosphorylation of LRP 5/6, followed by binding of Axin-1 or Axin-2 to the membrane complex as well. The deprivation of Axin from the β-catenin destruction complex leads to the disassembly of the latter and β-catenin can reach the nucleus, where it together with TCF and LEF transcription factors and other transcriptional coregulators like Pygopus, BCL9/Legless, CDK8 module of Mediator and TRRAP initiates transcription of genes with promoters containing TCF elements (Najdi, J. Carcinogenesis 2011; 10:5).
The Wnt signaling cascade can be constitutively activated by mutations in genes involved in this pathway. This is especially well documented for mutations of the APC and axin genes, and also for mutations of the β-catenin phosphorylation sites, all of which are important for the development of colorectal and hepatocellular carcinomas (Polakis, EMBO J., 31, 2012, 2737-2746).
The Wnt signaling cascade has important physiological roles in embryonal development and tissue homeostasis the latter especially for hair follicles, bones and the gastrointestinal tract. Deregulation of the Wnt pathway can activate in a cell and tissue specific manner a number of genes known to be important in carcinogenesis. Among them are c-myc, cyclin D1, Axin-2 and metalloproteases (He et al., Science 281, 1998, 1509-1512).
Deregulated Wnt activity can drive cancer formation, increased Wnt signaling can thereby be caused through autocrine Wnt signaling, as shown for different breast, ovarian, prostate and lung carcinomas as well as for various cancer cell lines (Bafico, Cancer Cell 6, 2004, 497-506; Yee, Mol. Cancer 9, 2010, 162-176; Nguyen, Cell 138, 2009, 51-62).
For cancer stem cells (CSCs) it was shown that they have increased Wnt signaling activity and that its inhibition can reduce the formation of metastases (Vermeulen et al., Nature Cell Biol. 12 (5), 2010, 468-476; Polakis, EMBO J. 31, 2012, 2737-2746; Reya, Nature, 434, 2005, 843-850).
Furthermore, there is a lot of evidence supporting an important role of Wnt signaling in cardiovascular diseases. One aspect thereby is heart failure and cardiac hypertrophy where deletion of Dapper-1, an activator of the canonical β-catenin Wnt pathway has been shown to reduce functional impairment and hypertrophy (Hagenmueller, M. et al.: Dapper-1 induces myocardial remodeling through activation of canonical wnt signaling in cardiomyocytes; Hypertension, 61 (6), 2013, 1177-1183).
Additional support for a role of Wnt signaling in heart failure comes from animal experimental models and clinical studies with patients, in which it was shown, that the level of secreted frizzled related protein 3 (sFRP3) is associated with the progression of heart failure (Askevold, E. T. et al.: The cardiokine secreted Frizzled-related protein 3, a modulator of Wnt signaling in clinical and experimental heart failure; J. Intern Med., 2014 (doi:10.1111/joim.12175)). For cardiac remodeling and infarct healing the expression of Fzd2 receptors on myofibroblasts migrating into the infarct area has been demonstrated (Blankesteijn, W. M. et al.: A homologue of Drosophila tissue polarity gene frizzled is expressed in migrating myofibroblasts in the infracted rat heart; Nat. Med. 3, 1997, 541-544). The manifold effects of Wnt signaling in heart failure, fibrosis and arrhythmias have been recently reviewed by Dawson et al. (Dawson, K. et al.: Role of the Wnt-Frizzled system in cardiac pathophysiology: a rapidly developing, poorly understood area with enormous potential; J. Physiol. 591 (6), 2013, 1409-1432).
For the vasculature, effects of Wnt signaling could be shown as well, mainly in respect to restenosis via enhancement of vascular smooth muscle cell proliferation (Tsaousi, A. et al.: Wnt4/b-catenin signaling induces VSMC proliferation and is associated with initmal thickening; Circ. Res. 108, 2011, 427-436).
Besides the effects on heart and vasculature, dysregulated Wnt signaling is also an important component in chronic kidney disease as could be shown for upregulated Wnt activity in immune cells from corresponding patients (Al-Chaqmaqchi, H. A. et al.: Activation of Wnt/b-catenin pathway in monocytes derived from chronic kidney disease patients; PLoS One, 8 (7), 2013, doi: 10.1371) and altered levels of secreted Wnt inhibitor in patient sera (de Oliveira, R. B. et al.: Disturbances of Wnt/b-catenin pathway and energy metabolism in early CKD: effect of phosphate binders; Nephrol. Dial. Transplant. (2013) 28 (10): 2510-2517).
In adults, mis-regulation of the Wnt pathway also leads to a variety of abnormalities and degenerative diseases. An LRP mutation has been identified that causes increased bone density at defined locations such as the jaw and palate (Boyden L M et al.: High bone density due to a mutation in LDL-receptor-related protein 5; N Engl J Med. 2002 May 16; 346(20):1513-21, Gong Y, et al.: LDL receptor-related protein 5 (LRP5) affects bone accrual and eye development; Cell 2001; 107:513-23). The mutation is a single amino-acid substitution that makes LRP5 insensitive to Dkk-mediated Wnt pathway inhibition, indicating that the phenotype results from overactive Wnt signaling in the bone. Recent reports have suggested that Wnt signaling is an important regulator for adipogenesis or insulin secretion and might be involved in the pathogenesis of type 2 diabetes. It has been shown that expression of the Wnt5B gene was detectable in several tissues, including adipose, pancreas, and liver. Subsequent in vitro experiments identified the fact that expression of the Wnt5b gene was increased at an early phase of adipocyte differentiation in mouse 3T3-L1 cells. Furthermore, overexpression of the Wnt5b gene in preadipocytes resulted in the promotion of adipogenesis and the enhancement of adipocytokine-gene expression. These results indicate that the Wnt5B gene may contribute to conferring susceptibility to type 2 diabetes and may be involved in the pathogenesis of this disease through the regulation of adipocyte function (Kanazawa A, et al.: Association of the gene encoding wingless-type mammary tumor virus integration-site family member 5B (Wnt5B) with type 2 diabetes; Am J Hum Genet. 2004 November; 75(5):832-43)
Accordingly, identification of methods and compounds that modulate the Wnt-dependent cellular responses may offer an avenue for regulating physiological functions and therapeutic treatment of diseases associated with aberrant activity of the pathways.
Inhibitors of the Wnt signalling pathway are disclosed e.g. in US2008-0075714(A1), US2011-0189097(A1), US2012-0322717(A9), WO2010/014948(A1), WO2012/088712(A1), WO2012/140274(A2,A3) and WO2013/093508(A2).
WO 2005/084368(A2) discloses heteroalkyl-substituted biphenyl-4-carboxylic acid arylamide analogues and the use of such compounds for treating conditions related to capsaicin receptor activation, for identifying other agents that bind to capsaicin receptor, and as probes for the detection and localization of capsaicin receptors. The structural scope of the compounds claimed in claim 1 is huge, whereas the structural space spanned by the few examples is much smaller. There is no specific example which is covered by the formula (I) as described and defined herein.
WO 2000/55120(A1) and WO 2000/07991 (A1) disclose amide derivatives and their use for the treatment of cytokine mediated diseases. The few specific examples disclosed in WO 2000/55120(A1) and WO 2000/07991 (A1) are not covered by the formula (I) as described and defined herein.
WO 1998/28282 (A2) discloses oxygen or sulfur containing heteroaromatics as factor Xa inhibitors. The specific examples disclosed in WO 1998/28282 (A2) are not covered by the formula (I) as described and defined herein.
WO 2011/035321 (A1) discloses methods of treating Wnt/Frizzled-related diseases, comprising administering niclosamide compounds. According to the specification of WO 2011/035321 (A1) libraries of FDA-approved drugs were examined for their utility as Frizzled internalization modulators, employing a primary imaged-based GFP-fluorescence assay that used Frizzled1 endocytosis as the readout. It was discovered that the antihelminthic niclosamide, a drug used for the treatment of tapeworms, promotes Frizzled1 internalization (endocytosis), down regulates Disheveled-2 protein, and inhibits Wnt3A-stimulated β-catenin stabilization and LEF/TCF reporter activity. The specific examples disclosed in WO 2011/035321 (A1) are not covered by the formula (I) as described and defined herein. Additionally, WO 2011/035321 (A1) does neither teach nor suggest the compounds of formula (I) as described and defined herein. The same is true for the related publication WO 2004/006906 (A2) which discloses a method for treating a patient having a cancer or other neoplasm by administering to the patient a niclosamide.
JP 2010-138079 (A) relates to amide derivatives exhibiting insecticidal effects. The specific examples disclosed in JP 2010-138079 (A) are not covered by the formula (I) as described and defined herein.
WO 2004/022536 (A1) relates to heterocyclic compounds that inhibit phosphodiesterase type 4 (PDE 4) and their use for treating inflammatory conditions, diseases of the central nervous system and insulin resistant diabetes. The specific examples disclosed in WO 2004/022536 (A1) are not covered by the formula (I) as described and defined herein.